a train is moving 35m/s to the east. it speeds up to 42 m/s east over the course of 40 seconds. what is the trains acceleration?
1 answer:
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Answer:
1) 1.31 m/s2
2) 20.92 N
3) 8.53 m/s2
4) 1.76 m/s2
5) -8.53 m/s2
Explanation:
1) As the box does not slide, the acceleration of the box (relative to ground) is the same as acceleration of the truck, which goes from 0 to 17m/s in 13 s
2)According to Newton 2nd law, the static frictional force that acting on the box (so it goes along with the truck), is the product of its mass and acceleration
3) Let g = 9.81 m/s2. The maximum static friction that can hold the box is the product of its static coefficient and the normal force.
So the maximum acceleration on the block is
4)As the box slides, it is now subjected to kinetic friction, which is
So if the acceleration of the truck it at the point where the box starts to slide, the force that acting on it must be at 136.6 N too. So the horizontal net force would be 136.6 - 108.3 = 28.25N. And the acceleration is
28.25 / 16 = 1.76 m/s2
5) Same as number 3), the maximum deceleration the truck can have without the box sliding is -8.53 m/s2
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1) First of all, since we know the radius of the wire (
), we can calculate its cross-sectional area
2) Then, we can calculate the current density J inside the wire. Since we know the current,
, and the area calculated at the previous step, we have
3) Finally, we can calculate the electric field E applied to the wire. Given the conductivity
of the aluminium, the electric field is given by
1) First of all, since we know the radius of the wire (
2) Then, we can calculate the current density J inside the wire. Since we know the current,
3) Finally, we can calculate the electric field E applied to the wire. Given the conductivity